A sonic or ultrasonic transducer, as described above, is already known from EP 0 615 471 B1. The known transducer especially distinguishes itself in that, when the dimensions of the piezoceramic disc are small, the transducer has a reduced operating frequency, as compared with the radial resonance frequency of the piezoceramic disc alone. This is achieved through a metal ring which surrounds the lateral surface of the piezoceramic disc with a form- and force-fit. For this, the metal ring is preferably assembled with the piezoceramic disc by shrink-fitting. Because of the coupling, the combination of the piezoceramic disc and the coupling ring behaves like a radial oscillator; especially, the surface of the radial oscillator, i.e. the surface formed from both components, acts as radiating surface for the sonic or ultrasonic waves.